1. Field of the Invention
The present invention relates to an SOI substrate in which an insulating portion contains nitrogen.
2. Description of the Related Art
The use of an SOI (Silicon On Insulator) substrate in which a silicon portion where a semiconductor element is to be formed is provided on an insulating portion is effective for improving the performance of a semiconductor device. Japanese Patent Laid-Open No. 2002-170942 discloses that, due to the fact that the insulating portion contains nitrogen, the diffusion of impurities to the silicon portion can be suppressed. Japanese Patent Laid-Open No. 2011-077504 discloses introducing nitrogen into the insulating portion by plasma nitridation treatment.
However, according to former techniques, even when nitrogen is introduced, the suppression of diffusion of impurities to the silicon portion has not been sufficient.